Digital subscriber loop (DSL)-based (packetized) communications allow telecommunication service providers to deliver multiple types of digital signalling channels (e.g., voice, data, video, and internet) at a fraction of the cost of conventional time division multiplexed (TDM)-based circuit switched networks. To deliver packetized voice and data, the service provider will typically deploy several different pieces of equipment (such as asynchronous transfer mode (ATM) switches, digital subscriber line access multiplexers (DSLAMs), voice gateways and the like) in the signal transport path from a central office to a customer premises-resident integrated access device (IAD).
For call routing control, the IAD contains a supervisory communications controller, which is programmed to interface telecommunication service (such as high speed T1 and integrated services digital network (ISDN) primary rate interface (PRI) traffic) between one or more network communication links ported to its network side and one or more customer premises equipment (CPE) ports on its user side. The interface signaling types do not necessarily match (for example, calls can originate on a loop start trunk and exit the IAD on a ground start trunk or PRI).
In the case of voice calls, the communications controller's control software will customarily contain a dialed number-based call routing mechanism through which outgoing voice calls from a user side interface may be routed to a called number via a preferred service provider based upon the phone number dialed. Conversely, incoming calls from the network side are routed to a user interface based upon the incoming number. The supervisory call routing and control routine may also accommodate standard channel bank fixed routing procedures, in which one or more prescribed ports will always be mapped to a predefined (DS0) port on another interface.
Now although the use of dialed number-based call routing provides an effective way to interface signaling traffic between various ports of a terminal unit, there are applications where it may be desired or necessary to route a call without the benefit of or even possibility of receiving dialed digits from the calling circuit.